Amplification of optical signals is often required in optical communication systems. Optical amplifiers can be implemented in optical fiber such as, for example, erbium doped fiber amplifiers (EDFAs), fiber Raman amplifiers. Such optical amplifiers can be useful in many optical fiber applications.
Optical amplifiers can also be implemented in semiconductor materials (e.g., semiconductor optical amplifiers or SOAs). However, SOAs tend to be low power, noisy and polarization sensitive.